CN217445271U

CN217445271U - Soft starter

Info

Publication number: CN217445271U
Application number: CN202221585604.3U
Authority: CN
Inventors: 牛玉环; 赵俊金; 孟凡斌; 刘桂敏; 燕明华
Original assignee: Heilongjiang Honghao Motor Manufacturing Co ltd
Current assignee: Heilongjiang Honghao Motor Manufacturing Co ltd
Priority date: 2022-06-23
Filing date: 2022-06-23
Publication date: 2022-09-16
Anticipated expiration: 2032-06-23

Abstract

The utility model discloses a soft starter, relating to a motor starter, aiming at solving the problem of low heat dissipation efficiency of a silicon plate in the existing motor soft starter, comprising a shell and a soft start control unit; the shell comprises a water-cooling back plate, and the water-cooling back plate comprises a water-cooling base plate and a water-cooling cover plate; the water-cooling substrate is positioned on the back surface of the shell; a starter heating module is fixed on the inner side surface of the water-cooling substrate, and a water channel is arranged on the outer side surface of the water-cooling substrate; the water channel is a groove communicated in a serpentine shape; the water-cooling cover plate is fixed on the outer side surface of the water-cooling base plate and seals the water channel; the outer side wall of the water-cooling cover plate is fixedly provided with a water inlet nozzle and a water outlet nozzle which are respectively communicated with the inlet and the outlet of the water channel; the soft start control unit is arranged in the shell.

Description

Soft starter

Technical Field

The utility model relates to a motor starter.

Background

The soft start generally adopts a voltage time slope mode and a starting current limiting function, and can also have a frequency modulation soft start function. The starting current is limited by a set value, so that the impact of the overlarge starting torque generated by direct starting or star/angle starting on a power grid can be reduced, and the impact on a mechanical transmission system when the motor is started is reduced. The product can be set to a hard start state according to the requirements of field conditions. The soft starter should have complete protection functions such as overload, short circuit, phase failure, leakage locking and the like.

The thyristor in the existing motor soft starter only works when starting and stopping, belonging to an intermittent working system; and in the novel mechanical structure, the silicon plate is generally arranged on the core frame or the shell of the body without cooling. The silicon plate directly radiates heat through the heat radiation plate, so that the heat radiation efficiency is low, and the silicon plate can not work for a long time. The service life of the product is short, and the thyristor and the vacuum contactor are frequently damaged, so that the normal production is influenced.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a soft starter in order to overcome the problem that silicon plate radiating efficiency is low among the current soft starter of motor.

The utility model discloses a soft starter, which comprises a shell and a soft start control unit;

the shell comprises a water-cooling back plate, and the water-cooling back plate comprises a water-cooling base plate and a water-cooling cover plate;

the water-cooling substrate is positioned on the back surface of the shell; a starter heating module is fixed on the inner side surface of the water-cooling substrate, and a water channel is arranged on the outer side surface of the water-cooling substrate; the water channel is a groove communicated in a serpentine shape;

the water-cooling cover plate is fixed on the outer side surface of the water-cooling base plate and seals the water channel; the outer side wall of the water-cooling cover plate is fixedly provided with a water inlet nozzle and a water outlet nozzle which are respectively communicated with the inlet and the outlet of the water channel;

the soft start control unit is arranged in the shell.

The beneficial effects of the utility model are that:

the novel silicon plate heat dissipation plate is directly arranged on the water cooling bottom plate special for the shell, heat dissipation efficiency is greatly improved through heat dissipation of the water cooling plate, the silicon plate can work for a long time, and working requirements of eight hours are met; the service life of the soft starter is more than three times of that of the common soft starter.

Drawings

Fig. 1 is a schematic structural diagram of a housing with a water-cooled back plate of a soft starter according to the present invention;

fig. 2 is a schematic side view of a water-cooling back plate of a soft starter according to the present invention;

fig. 3 is a schematic side view of a cross-sectional structure of a water-cooled back plate of a soft starter according to the present invention;

fig. 4 is a schematic structural view of a water-cooling substrate of a soft starter according to the present invention;

fig. 5 is a schematic structural view of a water-cooling back plate of the soft starter of the present invention;

fig. 6 is a schematic diagram of a circuit topology of a first starting unit in a soft starter according to the present invention;

fig. 7 is a schematic diagram of a circuit topology of a second starting unit in a soft starter according to the present invention;

fig. 8 is a schematic diagram of a combined circuit topology of a motor and a motor power supply in a soft starter according to the present invention;

fig. 9 is a schematic circuit diagram of a first soft start controller in the soft starter of the present invention;

fig. 10 is a schematic circuit diagram of a second soft start controller in the soft starter of the present invention; the second soft start controller is a soft start controller in the second starting unit.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

It should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict.

The present invention will be further described with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

In a first specific embodiment, the soft starter of the present embodiment includes a housing and a soft start control unit;

the shell comprises a water-cooling back plate 1, and the water-cooling back plate 1 comprises a water-cooling base plate 1-1 and a water-cooling cover plate 1-2;

the water-cooled substrate 1-1 is positioned on the back of the shell; a starter heating module is fixed on the inner side surface of the water-cooling substrate 1-1, and a water channel 2 is arranged on the outer side surface; the water channel 2 is a groove which is communicated in a snake-shaped linear shape;

the water-cooling cover plate 1-2 is fixed on the outer side surface of the water-cooling base plate 1-1 and seals the water channel 2; a water inlet nozzle 3 and a water outlet nozzle 4 are fixed on the outer side wall of the water-cooling cover plate 1-2, and the water inlet nozzle 3 and the water outlet nozzle 4 are respectively communicated with the inlet and the outlet of the water channel 2;

the soft start control unit is arranged in the shell.

Specifically, the main structural features of the soft starter of the present embodiment are as shown in fig. 1, and the external dimensions of the soft starter are as follows: length X width X height (1397mm X894X 1060 mm). The soft starter consists of a square shell and two box-type bodies arranged in the shell. To facilitate movement during use, a bracket is mounted to the bottom of the housing. The shell is divided into a main cavity and a wiring cavity. The front door of the main cavity is a plane clamping block type translation quick door opening mechanism. Reliable mechanical interlocking is arranged between the front door and the vacuum isolation phase change switch, so that the front door cannot be opened when the vacuum isolation phase change switch is in a switch-on position; when the front door is opened, the vacuum isolating reversing switch cannot be switched on by a conventional method. When the door is opened, the emergency stop button on the side wall of the main cavity is pressed, the two phase change switches are both rotated to the stop position, the locking rod is rotated to lock the reversing switch, the handle on the door is pulled, the front door can be moved out of the limit range of the stop block to the left side, and the front door can be rotated around the hinge on the left side until the front door is completely opened. When the door is closed, the operation is opposite to the operation, but attention needs to be paid to prevent the collision between the door body and the explosion-proof surface of the shell flange. Two box-type bodies are arranged in the main cavity, and each box-type body comprises a panel and a body box. The panel is provided with a protector, a pilot plug-in, a switch power supply, a control relay, a button switch, a safety device and an external cable plug (socket). The main body box is internally provided with a contactor, a transformer, a resistance-capacitance absorber and the like. The body box is arranged on a slideway of a bottom plate of the main cavity, a front door is opened to screw down M8 fixing bolts at two ends of the body box, then 3 load lines and 3 power lines on the upper side and the lower side of a bypass contactor KM1(KM2) in the body box are disassembled, and a control line plug is pulled down to draw out the body box along the slideway.

The casing door is provided with a hanging plate, and the upper part of the hanging plate is provided with a starting button, a stopping button, a reset button, an external leading cable plug or a socket and the like.

The hanging plate can rotate on the door body so as to be convenient for maintenance. The commutator and the silicon plate are respectively arranged on the right side and the back part in the shell. The main cavity door body is provided with ten button rods which are upward, downward, affirming/resetting, starting and stopping. The wiring cavity is arranged at the upper part of the shell. The connection of the wiring cavity cover plate and the shell is of a bolt fastening structure. The wiring terminal of the main loop and the control loop are arranged in the cavity, and six wiring ports for the main loop to enter and exit and six wiring ports for the control loop are arranged on the side surface. The wiring chamber is equipped with main loop and control circuit binding post, and its planar arrangement is: the right part is provided with 6M 24 main connecting terminals, two groups of the connecting terminals are connected in parallel and are arranged longitudinally in two groups; the left part has 6M 24 main terminals. Meanwhile, the terminal board is provided with five nine-core terminals, and three terminal rows are arranged on the terminal board and connected with the nine-core terminals to be used as intrinsic safety control lines and external leading contacts.

The key point of the present embodiment is that, as shown in fig. 2 to 5, a heat dissipation plate of a silicon plate (thyristor 8) is directly mounted on a water-cooled backplate 1 of a housing, and the silicon plate can be operated for a long time by dissipating heat through the water-cooled backplate 1.

The silicon plate is fixed on a water-cooling base plate 1-1 by bolts, a water channel 2 is arranged in the water-cooling base plate 1-1, the water channel 2 is sealed by a water-cooling cover plate 1-2, and a water-cooling back plate 1 (a water-cooling door) is arranged at the back of the shell.

The water inlet nozzle 3 (or the base of the water inlet nozzle 3) is fixed on the water-cooling cover plate 1-2 through screws, the water-cooling cover plate 1-2 is welded on the water-cooling base plate 1-1, the water-cooling cover plate 1-2 seals water flow, water enters the water channel 2, cooling water cools the water-cooling base plate 1-1 through the water channel 2, and the water-cooling base plate 1-1 cools the silicon plate again. So that the silicon plate can dissipate heat through the water flowing continuously during operation.

In this embodiment, a plurality of heat dissipation through holes 5 are distributed on the water-cooled cover plate 1-2.

Specifically, as shown in fig. 1 to 5, the heat dissipation efficiency of the silicon board can be further improved by providing the heat dissipation through-holes 5.

A best embodiment, which is a further description of the first embodiment, in the present embodiment, the soft start control unit includes a first start unit 6 and a second start unit 7, and the first start unit 6 and the second start unit 7 have the same structure;

the first starter unit 6 includes a first pilot circuit 6-1 and a first relay circuit 6-2;

the first pilot circuit 6-1 includes a pilot XD1, a double pole change-over switch SA1, a start button QA1, and a stop button TA 1;

two output ends of the first pilot loop power supply are respectively and electrically connected with an A3 port and a B3 port of a pilot XD1, and an A6 port of the pilot XD1 is respectively and electrically connected with a B6 port of the pilot XD1 through a switch of a double-pole change-over switch SA1, a start button QA1 and a stop button TA1 in sequence;

the first relay circuit 6-2 includes a switching power source UR1, a first soft start controller, and an intermediate relay ZJ 11;

the power output end of the first relay loop power supply is electrically connected with the power input end of the switching power supply UR1 and the power input end of the first soft start controller in parallel; the positive electrode of the switching power supply UR1 is electrically connected with the negative electrode of the switching power supply UR1 through the coil of the intermediate relay ZJ11 and the normally open contact of the pilot XD1 in sequence;

two ends of a first normally open contact of the intermediate relay ZJ11 are respectively and electrically connected with an A16 start-stop port and an A17 start-stop port of the first soft start controller;

the input and output control ends of each phase of thyristor of the first soft start controller are respectively and electrically connected with the output and input control ends of each phase of thyristor of the thyristor 8;

the power input end of the motor is electrically connected with the motor power supply through a thyristor 8, and the thyristor 8 is a starter heating module.

In this embodiment, the first relay circuit 6-2 further includes a coil of the intermediate relay ZJ12, a toggle switch NK11, and a toggle switch NK 12; the soft start control unit further comprises a first contactor loop 6-3;

the negative electrode of the switching power supply UR1 is electrically connected with the moving end of the button switch NK11, the soft-hard starting static contact of the button switch NK11 is electrically connected with the moving end of the button switch NK12, and the soft starting static contact of the button switch NK12 is electrically connected with the positive electrode of the switching power supply UR1 through the bypass relay of the first soft starting controller and the coil of the intermediate relay ZJ12 in sequence;

an online starting static contact of the button switch NK11 is electrically connected with the anode of the switching power supply UR1 through a hard starting static contact of the button switch NK12, a second normally open contact of the intermediate relay ZJ11 and a coil of the intermediate relay ZJ12 in sequence;

the first contactor loop 6-3 comprises the normally open contacts of ZJ12 and the coil of bypass contactor KM 1;

one end of the first contactor loop power supply is electrically connected with the movable end of a button switch NK11 through a normally open contact of ZJ12, and a soft and hard starting static contact of the button switch NK11 is also electrically connected with the other end of the first contactor loop power supply through a coil of a bypass contactor KM 1;

the normally open contact of bypass contactor KM1 is electrically connected between the motor power supply input and the motor power supply.

In this embodiment, the first relay circuit 6-2 further includes a temperature protection switch 6-2-1;

the temperature protection switch 6-2-1 comprises a temperature protection normally open contact and a temperature protection normally closed contact which are connected in series; and the two ends of the temperature protection normally open contact and the temperature protection normally closed contact which are connected in series are respectively connected with the two ends of the fault relay of the first soft start controller.

Specifically, the implementation mode has the functions of online full-voltage operation, energy-saving operation, low-speed operation and bypass operation, the key is that the functions are realized through the matching of a preset mode of the soft start controller and an external circuit, and the specific circuit topology structure schematic diagram is shown in fig. 6-10.

Similarly, the second starting unit 7 has the same structure as the first starting unit 6, and includes a second pilot circuit, a second relay circuit, and a second contactor circuit.

The basic operation of the present embodiment will be described below.

When the isolating and reversing switch GHK rotates to the positive position or the negative position, the power transformers T1 and T2 are electrified, and the

secondary side outputs

18V, 220V and 110V voltages.

Wherein 18V feeds the first pilot circuit 6-1 (or the second pilot circuit); 220V supply 07MF soft start controller and switch power supply (first soft start controller and switch power supply UR1, or second soft start controller and switch power supply UR 2); 110V is supplied to the contactor control loop (first contactor loop 6-3 or second contactor loop) in which the bypass contactor KM1(KM2) is located.

The soft starter takes three groups of anti-parallel high-power thyristor modules as a main loop soft start switch, and takes a 07MF multifunctional intelligent soft start controller (a first soft start controller or a second soft start controller) as a control core. In the starting process of the motor, the first soft start controller or the second soft start controller automatically controls the motor according to a curve (including frequency modulation starting) preset by a user, and ensures that the starting acceleration is controlled within the range of 0.1m/s2 a 0.3m/s2, so that the starting process is smoothly and reliably completed.

The soft start has a full-voltage online mode, a power saving mode, a low-speed mode and a bypass mode, wherein the power saving mode can intelligently adjust output voltage and current according to load change conditions, the consumption of electric energy is reduced to the minimum under the condition of meeting the requirement of sufficient power of a load, the highest power saving rate can reach more than 25% under the condition of light load, and the power saving effect is achieved when the running current is not more than 70% of rated current. The low speed mode is suitable for low load, such as low speed maintenance, low speed test, material transportation, belt installation (belt telescoping), and the like.

The full-voltage online mode, the power saving mode and the low-speed mode are all online modes, and after the soft start is finished, the thyristor module is conducted to continue running to different degrees according to set parameters; if the bypass mode is adopted, after the soft start is finished, the bypass contactor KM1(KM2) is closed, so that the motor is put into the full-voltage operation of the power grid. Specific operation mode setting and operation processes are exemplified as follows (taking the first starting unit 6 as an example):

1. selecting a full-pressure online mode: firstly, the double-pole change-over switch SA1 is switched to a remote control or a near control (as shown in FIG. 1, the double-pole change-over switch SA1 can be switched between two circuits, wherein one circuit is used for the remote control, and the other circuit is used for the near control), the button switch NK11 is switched to be on-line (on-line starting stationary contact), and the button switch NK12 can be at any position; the 'full voltage on-line' mode is selected at first in the secondary submenu of the protector, then the basic parameter setting is entered, the soft start time setting and the initial time setting are adjusted, the soft start time is set to be 10S, the initial voltage is 50%, and other parameters enter the corresponding option adjustment according to the parameter requirements.

The action process is as follows: when the start button QA1 is pressed, the pilot XD1 acts, the normally open contact of the pilot XD1 is closed, the intermediate relay ZJ11 is electrified, meanwhile, the start loop of the first soft start controller is switched on, the conduction angle of the thyristor 8 is controlled, the motor is started smoothly according to a set curve, after the soft start is finished, the thyristor 8 is switched on continuously, the control loop of the bypass contactor KM1 is in the off position, the bypass contactor is in the non-operating state, and the motor operates by switching on and operating the thyristor 8.

2. Selecting a power-saving mode: firstly, the double-pole change-over switch SA1 is switched to remote control or access control, the button switch NK11 is switched to on-line (on-line starting stationary contact), and the button switch NK12 can be arranged at any position; firstly, selecting a 'power saving' mode in a secondary submenu of the protector, then entering basic parameter setting, adjusting soft start time setting and initial time setting, setting and adjusting the soft start time to be 10S, and setting the initial voltage to be 50%; the power saving parameter can be set as follows according to the parameter requirement: power saving current threshold 75%; the lowest working voltage is 57%; the electricity-saving delay time is 2 seconds; the current return difference is set to be 2; a filter coefficient of 2; saving 20% of knee current; a voltage rise coefficient 13; after the minimum voltage modification 20 (the above parameters may be set according to practical experience, and the present embodiment is a factory value) parameter adjustment is completed: pressing the start button QA1 starts.

The action process is as follows: the pilot device XD1 acts, the normally open contact is closed, the intermediate relay ZJ11 is electrified, meanwhile, the starting loop of the soft start controller is connected, the conduction angle of the controllable silicon module is controlled, the motor starts smoothly according to a set curve, the controllable silicon module is continuously connected after the soft start action is finished, the bypass contactor KM1 controls the loop to be in a disconnected position, the bypass contactor is in an inoperative state, the motor is connected by the controllable silicon module during operation, the voltage is adjusted according to the power-saving current threshold value and other parameters, the motor operates at full voltage when the current exceeds the power-saving current threshold value, if the current is reduced, the motor can still enter the power-saving adjustment, and a new balance point is searched according to the load and the power matching of the motor.

The low-speed mode action process is the same as the action process, except that the correct adjustment of the corresponding parameters comprises the following steps:

low-speed voltage setting, low-speed power frequency time, low-speed intermittent time and low-speed frequency division time, wherein the low-speed mode is suitable for the time when the load is lower.

It has two modes:

A. low-speed intermittence: the operation is carried out in a constant pressure mode, the machine is stopped after the operation reaches the set time, and the machine is restarted after the time delay of the intermittent time, so that the reciprocating alternate operation is carried out. This mode can only be shut down manually.

B. Low-speed frequency division: the method is characterized in that the method operates in a rated 1/7 rotating speed mode according to a set seven-frequency-division torque output voltage, automatically stops when a set time is reached, and is different from a conventional frequency division operation mode in that frequency division is constant-voltage output in the mode.

3. Select "bypass soft start" mode: firstly, the double-pole change-over switch SA1 is switched to remote control or advance control, the button switch NK11 is switched to soft and hard (soft and hard starting stationary contact), and the button switch NK12 is switched to soft (soft starting stationary contact); the 'bypass' mode is selected at first in the secondary submenu of the protector, then the basic parameter setting is entered, the soft time setting and the initial time setting are adjusted, if the soft time setting is set to be 10S, the initial voltage is 50%, and other parameters enter the corresponding option adjustment according to the parameter requirements. The action process is as follows: the starting button QA1 is pressed, the pilot device XD1 acts, the normally open contact of the pilot device XD1 is closed, the intermediate relay ZJ11 is powered on, meanwhile, the soft starting controller starts a loop to be switched on, the conduction angle of the silicon controlled module is controlled, the motor starts smoothly according to a set curve, after the action is finished, the controller executes the closing of the bypass relay A20 and the switching of the bypass relay A21, the ZJ12 is powered on, the normally open contact of the bypass relay is closed, the bypass contactor KM1 controls the loop to be powered on to attract, the bypass contactor is switched on, and the full-pressure working state is achieved.

Two box-type bodies are arranged in the shell, and each box-type body comprises a panel and a body box. The panel of the box body is provided with a protector, a pilot plug-in, a switch power supply, a control relay, a button switch, a safety device and an external lead cable plug (socket) which are shown in figure 5.

The main body box is internally provided with a contactor, a transformer, a resistance-capacitance absorber and the like.

Wherein, the pilot assembly can adopt the existing pilot assembly.

The embodiment has the realization of the functions of online operation, energy-saving operation and low-speed operation on the line, and has the following effects:

A. the service life of the equipment can be greatly prolonged by online operation, and the functions of the power-saving mode and the low-speed mode are realized, so that the use range and the performance of the equipment are widened;

B. the power saving mode can intelligently adjust output voltage and current according to the load change condition, the consumption of electric energy is reduced to the minimum under the condition of meeting the requirement of enough power of a load, the highest power saving rate can reach more than 25% under the condition of light load, and the power saving effect is achieved when the running current is not more than 70% of rated current;

C. the low speed mode is suitable for low load, such as low speed maintenance, low speed test, material transportation, belt installation (belt telescoping), and the like.

D. The novel and inside components and parts of box body arrange and make the structure optimize more, even if be convenient for use, maintenance, assembly, realized the miniaturization again, it is aesthetic in appearance.

If the intelligent power-saving control device is used for dragging the underground belt conveyor, the output voltage and the output current are intelligently adjusted according to the load change condition in the power-saving mode, the consumption of electric energy can be reduced to the minimum under the condition of meeting the requirement of enough power of the load, the highest power-saving rate can reach more than 25% under the condition of light load, and the power-saving effect is achieved when the running current is not more than 70% of rated current.

When starting, the thyristor completes voltage regulation and current limitation to make the starting voltage and current gradually increase according to the set curve, and when reaching full voltage, the vacuum contactor operates by bypass.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims

1. A soft starter is characterized by comprising a shell and a soft start control unit;

the shell comprises a water-cooling back plate (1), and the water-cooling back plate (1) comprises a water-cooling base plate (1-1) and a water-cooling cover plate (1-2);

the water-cooled substrate (1-1) is positioned on the back of the shell; a starter heating module is fixed on the inner side surface of the water-cooling base plate (1-1), and a water channel (2) is arranged on the outer side surface; the water channel (2) is a groove communicated in a snake-shaped linear way;

the water-cooling cover plate (1-2) is fixed on the outer side surface of the water-cooling base plate (1-1) and seals the water channel (2); a water inlet nozzle (3) and a water outlet nozzle (4) are fixed on the outer side wall of the water-cooling cover plate (1-2), and the water inlet nozzle (3) and the water outlet nozzle (4) are respectively communicated with an inlet and an outlet of the water channel (2);

the soft start control unit is arranged in the shell.

2. A soft starter according to claim 1, characterized in that the water-cooled cover plate (1-2) is provided with a plurality of heat-dissipating through-holes (5) distributed over it.

3. A soft starter according to claim 1 or 2, characterized in that the soft start control unit comprises a first starting unit (6) and a second starting unit (7), and that the first starting unit (6) and the second starting unit (7) are of the same construction;

the first starting unit (6) comprises a first pilot circuit (6-1) and a first relay circuit (6-2);

the first pilot circuit (6-1) comprises a pilot XD1, a double-pole change-over switch SA1, a start button QA1 and a stop button TA 1;

the first relay loop (6-2) comprises a switching power supply UR1, a first soft start controller and an intermediate relay ZJ 11;

the power output end of the first relay loop power supply is electrically connected with the power input end of the switching power supply UR1 and the power input end of the first soft start controller in parallel; the positive electrode of the switching power supply UR1 is electrically connected with the negative electrode of the switching power supply UR1 through a coil of the intermediate relay ZJ11 and a normally open contact of the pilot device XD1 in sequence;

the input and output control ends of each phase of thyristor of the first soft start controller are respectively and electrically connected with the output and input control ends of each phase of thyristor of the thyristor (8);

the power supply input end of the motor is electrically connected with a motor power supply through a thyristor (8), and the thyristor (8) is a starter heating module.

4. A soft starter according to claim 3 characterized in that the first relay loop (6-2) further comprises the coil of the intermediate relay ZJ12, a toggle switch NK11 and a toggle switch NK 12; the soft start control unit further comprises a first contactor circuit (6-3);

the first contactor loop (6-3) comprises the normally open contacts of ZJ12 and the coil of the bypass contactor KM 1;

5. A soft starter according to claim 4 characterized in that the first relay loop (6-2) comprises a temperature protection switch (6-2-1);

the temperature protection switch (6-2-1) comprises a temperature protection normally open contact and a temperature protection normally closed contact which are connected in series; and the two ends of the temperature protection normally open contact and the temperature protection normally closed contact which are connected in series are respectively connected with the two ends of the fault relay of the first soft start controller.